1. Field of the Invention
The present invention relates to measurement-while-drilling and logging-while-drilling technologies used in the oil and gas industry, and more specifically to downhole mud pulse telemetry assemblies and downhole health monitoring systems.
2. Description of the Related Art
In downhole drilling operations, tools are lowered deep into the ground to perform various functions, such as drilling, measuring related data, and logging the data. Measurement-while-drilling (MWD) allows for the surface acquisition of downhole data during drilling. Boreholes may be thousands of feet in length, and may encompass different geological rock formations. Due to the length of the drill string, communication between surface equipment and downhole tools is limited during drilling applications. In modern measurement-while-drilling systems, information is telemetered to the surface primarily through either mud pulse, electromagnetic, or acoustic telemetry systems. These telemetry systems may transmit data regarding the location, orientation, and inclination of the drill string, the type of rock formation that is being drilled, the rotational speed of the drill string, etc.
Mud pulse telemetry systems are commonly used to communicate between a downhole tool and the uphole operator during drilling applications. Data to be transmitted is encoded into a predetermined encoding scheme. In mud pulse telemetry systems, a pulser is used to generate surges, or pulses, in the drilling fluid, generically known as mud, which is flowing through the drill string. The pulser generates pressure pulses by constricting a flow path in the fluid in the borehole. The constrictions are created and then released in the drill string with a specific timing to generate patterns to encode data based on the timing of the pressure pulses.
A common type of pulser is a hydraulic, or tensor, pulser. In a hydraulic pulser, pulser driver circuitry activates a solenoid. The solenoid actuation causes a pilot valve, which may be a poppet valve, to open, which causes a signal shaft to move and create another restriction at the bottom of the tool. This restriction causes a pulse to be generated through the fluid.
The pressure pulses propagate through the fluid from the downhole tool to the surface. Pressure sensitive transducers at the surface can detect the encoded pulses and decode the pulses to arrive at the original data. The real time capture and transmission of data allows operators at the surface to make real time decisions regarding drilling operations. The mud pulse telemetry communication may be bidirectional, and surface equipment may generate pulses that are telemetered downhole to steer or control a downhole drill string.
If any of these elements fail, the pressure pulse will either be distorted or not generated. Current systems have open loop monitoring capabilities and can only monitor whether the solenoid circuitry applied the appropriate power to activate the solenoid. Beyond this, current systems cannot determine if the solenoid, the pilot valve, or the signal shaft individually fails. Further, current systems cannot determine if a pulse was actually generated by the mud pulse telemetry assembly.